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141.
Nancy E. Ornelas-Soto Jorge L. Guzmán-Mar Pedro L. López de Alba Leticia López Martínez Oracio Barbosa-García Victor Cerdà Martín 《Mikrochimica acta》2009,167(3-4):273-280
A multisyringe flow injection system with spectrophotometric detection is presented as a fast, robust and low-reagent consumption system for the determination of azinphos methyl (AzMe) in water samples. Determination is based on the Griess reaction. The analyte is hydrolyzed and the reaction product reacts with nitrite in acid medium to form the diazonium salt that reacts further with 1-naphtol reagent to produce an azo compound. The azo derivative is spectrophotometrically monitored at 485 nm. The influence of several chemical and flow variables has been investigated. Under the optimum analytical conditions, the linearity of the calibration curve for AzMe ranges from 1 to 32 μg mL?1. The detection limit is 0.17?µg mL?1, and recoveries between 95 to 109% have been obtained. The repeatability (RSD) is 0.8% for a 10?μg mL?1 solution, and the injection throughput is seven samples h?1. The system has been satisfactorily applied to the determination of AzMe in spiked river and dam water samples. The results were in agreement at the 95% confidence level with those obtained by HPLC. 相似文献
142.
Aurélie Alba Aurélia Schopp Anne‐Paula De Sousa Delgado Roland Cherif‐Cheikh Blanca Martín‐Vaca Didier Bourissou 《Journal of polymer science. Part A, Polymer chemistry》2010,48(4):959-965
The bis‐sulfonamide m‐C6H4(SO2NHPh)2 efficiently promotes the ring‐opening polymerization of lactide when combined with tertiary amines, such as N,N‐dimethylaminopyridine. Polylactides of controlled molecular weights (Mn up to 17,700 g mol?1) and very narrow molecular weight distributions (Mw/Mn < 1.11) are obtained under mild conditions and in a living fashion. The reaction takes place through a bifunctional mechanism involving activation of both the alcohol and the monomer. Modulation of the sulfonamide component supports cooperative dual hydrogen‐bonding of lactide involving the two (SO2NHAr) moieties. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 959–965, 2010 相似文献
143.
C. von der Heide J. Brand W. Kerp A. Gautier P. Clausmann H. D. Gibbs C. C. James A. Hubert F. Alba K. Heumann J. Wiernik L. Medicus Chr. Mebold A. C. Langmuir E. W. T. Jones J. Ryder A. Greenwood W. Thomson J. P. Shenton und C. Strzyzowski 《Fresenius' Journal of Analytical Chemistry》1909,48(7-8):497-502
Ohne Zusammenfassung 相似文献
144.
This paper demonstrates the versatility of the class of chiral ligands naplephos, which has been further refined by preparing new ‘tagged’ versions for selective use in polar media (e.g., ionic liquids). These modified types, along with the best performing original varieties, have been examined in two Pd-catalysed asymmetric processes involving C-C and C-N bond formation. High ees have been achieved in traditional solvents, while the experiments performed in ionic liquids confirm the difficulty of predicting the outcome of a reaction in these media and the general decrease in the catalytic performance. 相似文献
145.
146.
Maria Alba Nicolas Pazos‐Perez Beln Vaz Pilar Formentin Moritz Tebbe Miguel A. Correa‐Duarte Pedro Granero Josep Ferr‐Borrull Rosana Alvarez Josep Pallares Andreas Fery Angel R. deLera Lluis F. Marsal Ramn A. Alvarez‐Puebla 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(25):6675-6675
147.
148.
Sara Sánchez-González Eva Pose-Juan Eliseo Herrero-Hernández Alba Álvarez-Martín Maria Jesús Sánchez-Martín 《International journal of environmental analytical chemistry》2013,93(15):1585-1601
This research has evaluated the agricultural impact of the use of pesticides in small agricultural areas in the Águeda river basin, which straddles the Spanish-Portuguese border. Sixteen pesticides frequently used in the area, including herbicides, fungicides and insecticides and some of their degradation products, were monitored in 52 groundwater samples and 42 soil samples taken around them, using a developed multi-residual analytical method based on SPE-LC-MS. Sampling was carried out in two different seasons (winter and summer). The results indicated the presence of pesticides at several levels, both in groundwaters and soils. Thirteen of the pesticides studied were detected in one or more of the groundwater samples analysed, but only three pesticides were detected in the soil samples. Terbuthylazine, cyprodinil, tebuconazole and chlorpyrifos were the pesticides most frequently detected in groundwaters, whereas terbuthylazine, metalaxyl and tebuconazole were the sole compounds detected in soils. The distribution of the concentrations in groundwaters indicated that up to 80% and 70% of the samples collected in the summer on the Spanish and Portuguese sides, respectively, exceed the quality standards of 0.1 µg L?1 for one or more individual compounds and, in turn, up to 64% and 40% exceed the quality standards of 0.5 µg L?1 for all compounds. The presence of pesticide residues in the groundwaters and soils analysed may well be explained by the use of these compounds in agricultural practices. 相似文献
149.
Pazos MC Castro MA Orta MM Pavón E Valencia Rios JS Alba MD 《Langmuir : the ACS journal of surfaces and colloids》2012,28(19):7325-7332
A family of organomicas was synthesized using synthetic swelling micas with high layer charge (Na(n)Si(8-n)Al(n)Mg(6)F(4)O(20)·XH(2)O, where n = 2, 3, and 4) exchanged with dodecylammonium and octadecylammonium cations. The molecular arrangement of the surfactant was elucidated on the basis on XRD patterns and DTA. The ordering conformation of the surfactant molecules into the interlayer space of micas was investigated by (13)C, (27)Al, and (29)Si MAS NMR. The arrangement of alkylammonium ions in these high-charge synthetic micas depends on the combined effects of the layer charge of the mica and the chain length of the cation. In the organomicas with dodecylammonium, a transition from a parallel layer to a bilayer-paraffin arrangement is observed when the layer charge of the mica increases. However, when octadecylammonium is the interlayer cation, the molecular arrangement of the surfactant was found to follow the bilayer-paraffin model for all values of layer charge. The amount of ordered conformation all-trans is directly proportional of layer charge. 相似文献
150.
Heras Ojea María José Pons Balagué Alba Reta Mañeru Daniel Carolina Sañudo E. 《Journal of nanoparticle research》2014,16(1):1-8
We have investigated the effect of thermal annealing on the diode characteristics of solution-processed novel core–shell coaxial n–p nanorods heterojunction consisting of n-type ZnO as a core and p-type CuS as a shell material. The values of turn-on-voltage, rectification ratio, reverse saturation current density, barrier height, and ideality factors have been improved as the as-prepared heterojunction is annealed at higher temperatures owing to the improvement in the interface between ZnO and CuS as evidenced from the high-resolution transmission electron microscopy. The X-ray diffraction results also confirm the improvement in the crystalline quality of ZnO and CuS through annealing. The experimental current–voltage data are consistent with the presence of dominating recombination-tunneling conduction occurring through the interface defect states between ZnO and CuS. The results demonstrate that an annealing process plays a dominant role in the interfacial defects which helps to modify the diode performance paving a way to cheaper electronic nanodevices. 相似文献